1. Field of the Invention
The present invention relates to a composite metallic magnetic powder and a manufacturing method of the same used for high density magnetic recording, a magnetic painting, magnetic powder for magnetic therapy, and a magnetic recording medium.
2. Description of Related Art
Further higher recording density is desired in accordance with increase in capacity of the magnetic recording medium, represented by the one used for the purpose of backup of data in a computer. In order to achieve a high recording density, it appears that a magnetic powder with small particle volume is requested. In order to respond to such a request, after examination regarding metallic magnetic powder, inventors of the present invention disclose patent documents 1 to 3, and so forth.
Patent document 1 discloses a ferromagnetic iron alloy powder for magnetic recording medium, comprising acicular particles having an average major axis diameter (X) of 20 nm or larger and 80 nm or smaller, having an oxygen content of 15 wt. % or larger and a coercive force (Hc) of 0.0036X3−1.1X2+110X−1,390 (Oe) or larger.
Patent document 2 discloses a technique of improving magnetic characteristics per unit volume, by dissolving and removing a non-magnetic component that exists on the surface of the metallic magnetic powder, by using a reducing agent, etc.
As a development of the patent document 2, patent document 3 discloses a technique of forming a layer of carbon on the surface of the metallic magnetic particle by coating the surface of the metallic magnetic particle with an organic matter and applying re-reduction treatment thereto.    (Patent document 1) Japanese Patent Laid Open Publication No.2003-263720    (Patent document 2) Japanese Patent Laid Open Publication No.2007-294841    (Patent document 3) Japanese Patent Laid Open Publication No.2009-084600